Exchange length guidewires are often used during procedures in interventional radiology, including interventional cardiology, interventional neuroradiology, and interventional peripheral radiology.
The exchange length guidewires are used to facilitate exchanging of devices such as catheters or microcatheters, over a guidewire where, e.g., the physician removes a first microcatheter from a guidewire that is positioned at a site of interest and then advances a second microcatheter over the guidewire to that site in the vasculature.
For example, a physician may replace the original microcatheter with another catheter or a separate device having different properties or better suited for the intended procedure (e.g. better condition, more navigable, better supporting, etc.). For example, a first microcatheter can be used with properties that allow for accessing or navigation to the target site but a second microcatheter might be better suited to support or provide access for medical devices to the target site. Regardless, a physician performs a procedure for catheter exchange by placing a first microcatheter at a desired location within the vasculature often using a standard guidewire. Next, the physician removes the standard guidewire from the first microcatheter while leaving the first microcatheter at the site. The physician then inserts an exchange length guidewire (usually 280 cm to 300 cm in length) through the first microcatheter and positions a distal end of the exchange length guidewire at the intended site.
Once this exchange length guidewire is loaded into the microcatheter and positioned in the anatomy, the first microcatheter can be removed and replaced with a different microcatheter. The extra length of the exchange length guidewire enables the removal and replacement of the microcatheter (referred to as an exchange procedure) without loss of direct access to the proximal end of the guidewire by the physician.
The physician must perform an exchange procedure with caution because excessive movement of the tip of the exchange guidewire can cause irritation or even damage to the vessel. This is especially true for delicate vasculature such as the neurovasculature. In some extreme cases, excessive movement of the guidewire tip can perforate the vessel wall during the exchange procedure. Because of this, the exchange procedure typically takes place very slowly, where the physician removes the first microcatheter in incremental movements by holding the proximal end of the exchange guidewire and while simultaneously trying to prevent excessive movement of the exchange guidewire. Once the physician removes the first microcatheter, the physician advances a second microcatheter over the exchange guidewire and navigates the second microcatheter distally again while holding the proximal end of the guidewire and preventing as much motion as possible.
However, even with near immobilization of the proximal end of the guidewire, the distal end of the guidewire may still move more than desired. This unwanted motion can be the result of imprecise holding of the guidewire, or the result of the advancement of the microcatheter which causes undesired motion of the guidewire, or the result of patient movement during the breathing cycle, etc.
In any case, it is this unintended motion of the distal end of the guidewire that can cause the vessel irritation, spasm, dissection, and/or perforation. Physicians often curve the distal end of the guidewire to attempt to make it less traumatic; this practice may help somewhat but it may not lower the risk of vessel damage sufficiently. For example, as shown in FIG. 1, a microcatheter 12 advances along a guidewire 14 having a “J-tip” or “J-curve” 16. However, the J-curve 16 does not distribute the force sufficiently and can cause trauma to the walls of the vessel 10 along the portion of the guidewire 14 that is shaped into the curve 16.